Piston and rod connection



Aug. 14, 1956 FIG 2 United States Patent O PISTON AND ROD CONNE'CTION Julius Naab, Easton, Pa., assignor to Ingersoll-Rand 'Company, New York, N. Y., a corporation of New Jersey Application December 1, 1953, 'Serial No. 395,421 3 vClaims. (Cl. 309-17) This invention relates to pistons, and more particularly to a connection for securing a rod to a piston.

The invention is particularly suitable for use in a piston assembly the piston and rod of which, are threadedly connected together and constructed of metals having different coeficients of expansion, as for example an aluminum piston and a steel rod.

In Structures of this type, the relatively high coefiicient of expansion of the piston tends to loosen the threaded connection and makes it possible for the piston to rotate upon the rod. Various expedients aimed at obviating an occurrence of this nature have been deviced heretofore as, for example, by providing the piston and the rod with cooperating tapered portions or by the use of intricate cla-mping devices for securing the rod to the piston, but these have been found to be unsatisfactory from a mechanical standpoint and often highly objectionable because -of the high cost of production of the assembly.

It is accordingly an object of the present invention to lock the rod to the piston in a simplified and inexpensive manner and thereby obviate the need of tedious and costly construction to maintain a :stable connection between the two.

A more specific object of the invention is to assure the retention of the piston in the correct assembled position upon the rod.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawings accompanying this -specification and in which similar reference numera-ls refer to similar parts,

Figure l is a side elevation, partly broken away, of a piston assembly constructed in accordance with the practice of the invention,

Fig. 2 is a similar view, somewhat enlarged, showing the precise manner in which the various parts of the assembly are looked together, and

Pigs. 3 and 4 are transverse views taken through Fig. 2 on the lines 3-3 and 4-4, respectively, looking in the directions indicated by the arrows Referring more particularly to the drawings, 20 designates, in general, the piston assembly constructed in accordance with the practice of the invention and comprising a piston 21, a rod 22 and a looking member 23 for looking the piston 21 mimovably to the rod.

The piston 21 is shown as having end heads 24 and a central hub 25 formed integrally with the heads 24 and supported by ribs 26 Which radiate from the hub 25 and may extend to the cylindrical Wall of the piston. The hub 25 has a bore 27 and is recessed as at 28 in the intermediate portion thereof, and the part 29 of the bore 27 lying on one side of the recess 28 is formed for intimate engagement with a corresponding portion 30 of the rod 22.

The remaining portion of the bore 27 is also of uniform diameter through-out its length and is provided With threads 31 for cooperation with corresponding threads 32 on the end portion of the rod 22. The free end 33 of the rod lies short of the end of the threaded portion of the bore 27 and in the end of the piston adjacent thereto is ICC a recess 34 which is positioned coaxally with the bore 27 for the reception of a looking member 35 serving to hold the piston in a fixed position upon the rod 22.

The locking member 35 comprises a head 36 that seats at one end against the bottom 37 of the recess 34 and is preferably of no greater length than the depth of the recess. On the side of the head 36 confronting the rod 22 is a stem 39 having threads 40 for cooperation with the threads 41 of an aperture 42 formed axially in the end portion of the rod 22. The threads 40 of the stem 39 are of a considerably finer pitch than the threads 31 and 32 (as for example in the ratio of 2 to 1), tol assure against rotational movement of the piston upon the rod.

The head 36 is yof cylindrical form and is provided in its outer |surface with apertnres 43 for the accommodation of the prongs of a spanner wrench or other suitable tool whereby the looking member may be threaded into the rod 22.

The locking member is itself restrained against rotary movement as, for example, by a pin 44 which is embedded in the piston 21 and in engagement with a notch 45 in the periphery yof the head 36. The pin 44 is retained within the piston 21 by peening some of the material of the piston over the outer end of the pin, as indicated at 46. The lockng member will then be held fixedly against rotational movement and owing to the difference in the pitches iof the threads on the rod and the looking member the rod will be incapable of rotating relatively to the locking member.

In assembling the device, the rod 23 is fir-st threaded into the bore 27 to a point where its end 33 lies :short of the bottom 37 of the recess 34 in order to avoid contact of the rod with the head 36 of the |looking member 35. The locking member is then threaded into the rod to bring the head 36 into firm frictional engagement with the bottom surface 37 of the recess. The leading surfaces of the threads 32 are thereby drawn firmly into engagement With the opposed surfaces of the threads 31. After these parts are thus positioned, the hole in the piston which accommodates the pin 44 and the notch 45 are formed to assure true registry of the two and the pin 44 is then placed and secured in position.

As Will be readily apparent from the foregoing description, by thus looking the piston to the rod and securing the locking member against movement relatively to both all the parts of e assembly Will remain in the correct Without the need of intricate and costly machining of any of the parts vof the assembly.

I claim:

the threaded opening, and a looking member having a stem threaded into the threaded aperture and having a head seated against the piston for holding the rod against rotary movement with respect to the piston, and means positively engaging the looking member against rotation relative to the piston.

2. In combination, a piston having a threaded opening extending axially thereof and a recess at one end of the opening, a rod threaded into the opening having a threaded aperture extending endwise thereof and the threads of said aperture being of the same hand and of a different pitch than the threads of the threaded opening, and a looking member threaded into the aperture' having a head to lie in the recess and seat agains't'zthe'piston for holding the rod again-st rotary movementfwithrespect to the piston.

jpston .interlockingly engaging 3. Ivnneornbi'natonta piston having a threarled opening extending axia'lly thereof and a reess having Va s'eating surface coaxial with and atone end of the opening, a rod thnended .into the opening to a point short the senting sunfae, said 4roghaving 4a t'hreaded .apexnne extending endwispe thereof and .the threads tof .vsa'id aperinne being of a iner pitch than the threads of .the threaded opening, a looking member threadeinto epuerture having Ia head .to lie Within the recess .anfl sent-against theseating surface for .holding .the rod Vagainst rotary movement W'ith 'respect to the piston, .and means in .the .the looking member for holding .said :locking member against rotary movement with respect .to the HReferelklces'Cited in the file of Vthis patent UNITED STATES PATENTS Booth Apr. 17, Gott1ieb Nov. 1, Cable Dec. 30, Dona1ds-on. -r Apr. 18, Lee Jan. 18, Wolqens t :'Bec. 12, Hamilton et al. Dec. 3.1, Heges Aun. '12,

FOREIGN PATENTS Greatn'Britain June 10; 

